1. Field of the Invention
The present invention relates to a Schottky barrier diode and in particular to a Schottky barrier diode, having a low onset voltage without sacrificing breakdown voltage.
2. Description of the Related Art
Recently, Schottky barrier diodes are commonly applied to switching power supplies. Under the high switching frequency, in order to enhance the efficiency of switching power supplies, there is a need to improve the characteristics of the components adopted by switching power supplies, for example, the conduction loss of Schottky barrier diodes. Therefore, the characteristics of the Schottky barrier diode focus on two parts. The first part is the onset voltage and the second part is the breakdown voltage. In more specific terms, due to the higher onset voltage (such as 1V˜1.5 V) of the conventional AlGaN/GaN Schottky barrier diode, the conduction loss is serious. The structure of the Schottky barrier diode has to be improved for resolving the above-mentioned problems.
With regard to the structure of the Schottky barrier diode, generally, the Schottky barrier diode has an anode and a cathode. The junction formed between the metal arranged to be the anode of the Schottky barrier diode and the barrier layer of the Schottky barrier diode is the Schottky contact. The junction formed between the metal arranged to be the cathode and the barrier layer of the Schottky barrier diode is the ohmic contact. Gallium nitride (GaN) devices are commonly applied to fabricate conventional Schottky barrier diodes, and however there are some drawbacks in the GaN devices. For example, metal spiking can occur around the region of the ohmic contact, such that a high electric field is produced in the local regions, further resulting in the early breakdown of the GaN Schottky barrier diode. Moreover, the fabrication of the ohmic resistance is relatively difficult and therefore it is more difficult to yield good ohmic characteristics because the GaN material is a wide bandgap semiconductor. Finally, for the same reasons (i.e. GaN material being the wide bandgap semiconductor), the onset voltage of the GaN device is usually higher (about 1 V˜2 V), such that the whole efficiency of the electronic system becomes worse.
In view of this, there is a need to present a new Schottky barrier diode for resolving the problems in which the conventional Schottky barrier diode reduces the onset voltage, but sacrificing the breakdown voltage.